The Components That Make Up Scuba Equipment

Mandatory equipment used on every dive
A tank of compressed air carried by the diver on his or her back.
A first stage regulator attached to the tank that serves to lower air pressure delivered to the diver.
A second stage demand regulator and mouthpiece, which delivers air on inhalation and closes on exhalation.
A face mask that covers the diver’s eyes and nose, to allow for both underwater vision and equalization of air pressure within the mask.

An extra second stage regulator and mouthpiece, carried by the diver in case of emergency (when attached to a long hose, this extra second stage is called an octopus).
A submersible gauge to display an accurate depth and remaining air pressure in the tank.
A buoyancy control device (BCD) worn to provide a means of establishing positive buoyancy when needed.
A weight belt or integrated weight system to offset the positive buoyancy of the diver and scuba apparatus.
Fins to facilitate self-propulsion in the water.
Exposure suit or wet suit to prevent hypothermia as well as cuts and abrasions under water. In cold water gloves and a hood should be worn for hypothermia protection.

Optional equipment used on dives
snorkel
dive knife
small tank of extra air
dive computer
compass
dive lights
writing slate
whistle
inflatable signaling device

Depending on the circumstances, some of these items are essential. For example a night dive requires underwater flashlights, a snorkel for surface swimming, etc., however, they are not part of basic scuba equipment.

The Differences Between Recreational Scuba Diving and Other Forms of Scuba Diving

Recreational scuba diving, as taught by national certifying agencies, is defined as diving that uses only compressed air as the breathing mixture, is never done solo, does not exceed a depth of 130 feet, has a depth-time profile not requiring a decompression stop and does not require specialized training beyond the basic open water course.